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  <div class="section" id="module-binascii">
<span id="binascii-convert-between-binary-and-ascii"></span><h1>19.8. <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal"><span class="pre">binascii</span></code></a> — Convert between binary and ASCII<a class="headerlink" href="#module-binascii" title="Permalink to this headline">¶</a></h1>
<hr class="docutils" id="index-0" />
<p>The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal"><span class="pre">binascii</span></code></a> module contains a number of methods to convert between
binary and various ASCII-encoded binary representations. Normally, you will not
use these functions directly but use wrapper modules like <a class="reference internal" href="uu.html#module-uu" title="uu: Encode and decode files in uuencode format."><code class="xref py py-mod docutils literal"><span class="pre">uu</span></code></a>,
<a class="reference internal" href="base64.html#module-base64" title="base64: RFC 3548: Base16, Base32, Base64 Data Encodings; Base85 and Ascii85"><code class="xref py py-mod docutils literal"><span class="pre">base64</span></code></a>, or <a class="reference internal" href="binhex.html#module-binhex" title="binhex: Encode and decode files in binhex4 format."><code class="xref py py-mod docutils literal"><span class="pre">binhex</span></code></a> instead. The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal"><span class="pre">binascii</span></code></a> module contains
low-level functions written in C for greater speed that are used by the
higher-level modules.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p><code class="docutils literal"><span class="pre">a2b_*</span></code> functions accept Unicode strings containing only ASCII characters.
Other functions only accept <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like objects</span></a> (such as
<a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal"><span class="pre">bytes</span></code></a>, <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal"><span class="pre">bytearray</span></code></a> and other objects that support the buffer
protocol).</p>
<div class="last versionchanged">
<p><span class="versionmodified">Changed in version 3.3: </span>ASCII-only unicode strings are now accepted by the <code class="docutils literal"><span class="pre">a2b_*</span></code> functions.</p>
</div>
</div>
<p>The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal"><span class="pre">binascii</span></code></a> module defines the following functions:</p>
<dl class="function">
<dt id="binascii.a2b_uu">
<code class="descclassname">binascii.</code><code class="descname">a2b_uu</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_uu" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a single line of uuencoded data back to binary and return the binary
data. Lines normally contain 45 (binary) bytes, except for the last line. Line
data may be followed by whitespace.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.b2a_uu">
<code class="descclassname">binascii.</code><code class="descname">b2a_uu</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_uu" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert binary data to a line of ASCII characters, the return value is the
converted line, including a newline char. The length of <em>data</em> should be at most
45.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.a2b_base64">
<code class="descclassname">binascii.</code><code class="descname">a2b_base64</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_base64" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a block of base64 data back to binary and return the binary data. More
than one line may be passed at a time.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.b2a_base64">
<code class="descclassname">binascii.</code><code class="descname">b2a_base64</code><span class="sig-paren">(</span><em>data</em>, <em>*</em>, <em>newline=True</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_base64" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert binary data to a line of ASCII characters in base64 coding. The return
value is the converted line, including a newline char if <em>newline</em> is
true.  The output of this function conforms to <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc3548.html"><strong>RFC 3548</strong></a>.</p>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.6: </span>Added the <em>newline</em> parameter.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="binascii.a2b_qp">
<code class="descclassname">binascii.</code><code class="descname">a2b_qp</code><span class="sig-paren">(</span><em>data</em>, <em>header=False</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_qp" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a block of quoted-printable data back to binary and return the binary
data. More than one line may be passed at a time. If the optional argument
<em>header</em> is present and true, underscores will be decoded as spaces.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.b2a_qp">
<code class="descclassname">binascii.</code><code class="descname">b2a_qp</code><span class="sig-paren">(</span><em>data</em>, <em>quotetabs=False</em>, <em>istext=True</em>, <em>header=False</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_qp" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert binary data to a line(s) of ASCII characters in quoted-printable
encoding.  The return value is the converted line(s). If the optional argument
<em>quotetabs</em> is present and true, all tabs and spaces will be encoded.   If the
optional argument <em>istext</em> is present and true, newlines are not encoded but
trailing whitespace will be encoded. If the optional argument <em>header</em> is
present and true, spaces will be encoded as underscores per RFC1522. If the
optional argument <em>header</em> is present and false, newline characters will be
encoded as well; otherwise linefeed conversion might corrupt the binary data
stream.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.a2b_hqx">
<code class="descclassname">binascii.</code><code class="descname">a2b_hqx</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_hqx" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert binhex4 formatted ASCII data to binary, without doing RLE-decompression.
The string should contain a complete number of binary bytes, or (in case of the
last portion of the binhex4 data) have the remaining bits zero.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.rledecode_hqx">
<code class="descclassname">binascii.</code><code class="descname">rledecode_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.rledecode_hqx" title="Permalink to this definition">¶</a></dt>
<dd><p>Perform RLE-decompression on the data, as per the binhex4 standard. The
algorithm uses <code class="docutils literal"><span class="pre">0x90</span></code> after a byte as a repeat indicator, followed by a count.
A count of <code class="docutils literal"><span class="pre">0</span></code> specifies a byte value of <code class="docutils literal"><span class="pre">0x90</span></code>. The routine returns the
decompressed data, unless data input data ends in an orphaned repeat indicator,
in which case the <a class="reference internal" href="#binascii.Incomplete" title="binascii.Incomplete"><code class="xref py py-exc docutils literal"><span class="pre">Incomplete</span></code></a> exception is raised.</p>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.2: </span>Accept only bytestring or bytearray objects as input.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="binascii.rlecode_hqx">
<code class="descclassname">binascii.</code><code class="descname">rlecode_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.rlecode_hqx" title="Permalink to this definition">¶</a></dt>
<dd><p>Perform binhex4 style RLE-compression on <em>data</em> and return the result.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.b2a_hqx">
<code class="descclassname">binascii.</code><code class="descname">b2a_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_hqx" title="Permalink to this definition">¶</a></dt>
<dd><p>Perform hexbin4 binary-to-ASCII translation and return the resulting string. The
argument should already be RLE-coded, and have a length divisible by 3 (except
possibly the last fragment).</p>
</dd></dl>

<dl class="function">
<dt id="binascii.crc_hqx">
<code class="descclassname">binascii.</code><code class="descname">crc_hqx</code><span class="sig-paren">(</span><em>data</em>, <em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.crc_hqx" title="Permalink to this definition">¶</a></dt>
<dd><p>Compute a 16-bit CRC value of <em>data</em>, starting with <em>value</em> as the
initial CRC, and return the result.  This uses the CRC-CCITT polynomial
<em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>5</sup> + 1, often represented as
0x1021.  This CRC is used in the binhex4 format.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.crc32">
<code class="descclassname">binascii.</code><code class="descname">crc32</code><span class="sig-paren">(</span><em>data</em><span class="optional">[</span>, <em>value</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#binascii.crc32" title="Permalink to this definition">¶</a></dt>
<dd><p>Compute CRC-32, the 32-bit checksum of <em>data</em>, starting with an
initial CRC of <em>value</em>.  The default initial CRC is zero.  The algorithm
is consistent with the ZIP file checksum.  Since the algorithm is designed for
use as a checksum algorithm, it is not suitable for use as a general hash
algorithm.  Use as follows:</p>
<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="nb">print</span><span class="p">(</span><span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;hello world&quot;</span><span class="p">))</span>
<span class="c1"># Or, in two pieces:</span>
<span class="n">crc</span> <span class="o">=</span> <span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot;hello&quot;</span><span class="p">)</span>
<span class="n">crc</span> <span class="o">=</span> <span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="sa">b</span><span class="s2">&quot; world&quot;</span><span class="p">,</span> <span class="n">crc</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s1">&#39;crc32 = </span><span class="si">{:#010x}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">crc</span><span class="p">))</span>
</pre></div>
</div>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.0: </span>The result is always unsigned.
To generate the same numeric value across all Python versions and
platforms, use <code class="docutils literal"><span class="pre">crc32(data)</span> <span class="pre">&amp;</span> <span class="pre">0xffffffff</span></code>.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="binascii.b2a_hex">
<code class="descclassname">binascii.</code><code class="descname">b2a_hex</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_hex" title="Permalink to this definition">¶</a></dt>
<dt id="binascii.hexlify">
<code class="descclassname">binascii.</code><code class="descname">hexlify</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.hexlify" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the hexadecimal representation of the binary <em>data</em>.  Every byte of
<em>data</em> is converted into the corresponding 2-digit hex representation.  The
returned bytes object is therefore twice as long as the length of <em>data</em>.</p>
</dd></dl>

<dl class="function">
<dt id="binascii.a2b_hex">
<code class="descclassname">binascii.</code><code class="descname">a2b_hex</code><span class="sig-paren">(</span><em>hexstr</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_hex" title="Permalink to this definition">¶</a></dt>
<dt id="binascii.unhexlify">
<code class="descclassname">binascii.</code><code class="descname">unhexlify</code><span class="sig-paren">(</span><em>hexstr</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.unhexlify" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the binary data represented by the hexadecimal string <em>hexstr</em>.  This
function is the inverse of <a class="reference internal" href="#binascii.b2a_hex" title="binascii.b2a_hex"><code class="xref py py-func docutils literal"><span class="pre">b2a_hex()</span></code></a>. <em>hexstr</em> must contain an even number
of hexadecimal digits (which can be upper or lower case), otherwise an
<a class="reference internal" href="#binascii.Error" title="binascii.Error"><code class="xref py py-exc docutils literal"><span class="pre">Error</span></code></a> exception is raised.</p>
</dd></dl>

<dl class="exception">
<dt id="binascii.Error">
<em class="property">exception </em><code class="descclassname">binascii.</code><code class="descname">Error</code><a class="headerlink" href="#binascii.Error" title="Permalink to this definition">¶</a></dt>
<dd><p>Exception raised on errors. These are usually programming errors.</p>
</dd></dl>

<dl class="exception">
<dt id="binascii.Incomplete">
<em class="property">exception </em><code class="descclassname">binascii.</code><code class="descname">Incomplete</code><a class="headerlink" href="#binascii.Incomplete" title="Permalink to this definition">¶</a></dt>
<dd><p>Exception raised on incomplete data. These are usually not programming errors,
but may be handled by reading a little more data and trying again.</p>
</dd></dl>

<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a class="reference internal" href="base64.html#module-base64" title="base64: RFC 3548: Base16, Base32, Base64 Data Encodings; Base85 and Ascii85"><code class="xref py py-mod docutils literal"><span class="pre">base64</span></code></a></dt>
<dd>Support for RFC compliant base64-style encoding in base 16, 32, 64,
and 85.</dd>
<dt>Module <a class="reference internal" href="binhex.html#module-binhex" title="binhex: Encode and decode files in binhex4 format."><code class="xref py py-mod docutils literal"><span class="pre">binhex</span></code></a></dt>
<dd>Support for the binhex format used on the Macintosh.</dd>
<dt>Module <a class="reference internal" href="uu.html#module-uu" title="uu: Encode and decode files in uuencode format."><code class="xref py py-mod docutils literal"><span class="pre">uu</span></code></a></dt>
<dd>Support for UU encoding used on Unix.</dd>
<dt>Module <a class="reference internal" href="quopri.html#module-quopri" title="quopri: Encode and decode files using the MIME quoted-printable encoding."><code class="xref py py-mod docutils literal"><span class="pre">quopri</span></code></a></dt>
<dd>Support for quoted-printable encoding used in MIME email messages.</dd>
</dl>
</div>
</div>


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